Generally, the B. americanus is short and fat in body, with a short broad head and broadly circular snout. It's underbelly is granular, and the back is covered with different-sized warts. There are three or four pairs of dark spots down the back, each accompanied by one large wart. The eyes are prominent. The arms and legs are tubular and warty. They are generally olive in color, with parotoids and a brown crest.

Males are roughly 54-85 mm in length. Their back, sides and tympanum are of a dull citrine color with olive-citrine or yellow olive color on their hind legs and forelegs. The whole pectoral region is covered with scattered black spots, and these spots occur over the entire venter except for the throat and the center of the rear belly. There is some apricot-yellow color across the arm insertion. The pupil is rimmed with a citron yellow color.

Females are roughly 56-110 mm in length. The back is of a light brownish or buffy olive. The bigger warts are on the back, and the warts are in the centers of buffy brown colored spots. There is a stripe down the middle of the back, of a deep-olive buff color, yellow, or vinaceous-fawn, that leads from parotoid to groin. In the center of the breast, there is a dark spot (Wright 1949).